Normal Amplitude of Clean SH4131 Movement

[sorginator]

Hey everyone, I have a pretty technical question for anyone who might have more knowledge than I. For reference, I am going to be referencing this post by ctime about a part-by-part comparison of the gen 4131 vs SH4131 movements.

If you look at the comparison, you can see that there are some very minor differences in that the escape wheel is not skeletonized, and the pallet fork is thicker on the SH4131. Although very minutely different, the parts are heavier, and as such have greater inertia. This means that less energy is being transmitted to the balance wheel with every vibration, since the spring has to overcome the inertial force of the parts before applying force to the balance wheel.

I've tried looking for a comparison between the amplitude of gen 4131 vs SH4131, but I can't seem to find any information, but basic understanding of forces would indicate that the amplitude of the balance wheel would be less than on gen. I know that this isn't necessarily a bad thing, and I know that solid escape wheels and pallet forks have been used for quite literally hundreds of years, but the question still remains: In a movement designed to have less inertia, does this mean that a potentially lower amplitude of the balance wheel in the SH4131 results in less accuracy when taking into account wrist movements throughout the day? I understand that the timing and beat error can be regulated, and that Clean has probably thought of, and compensated for this by reducing the tension on the hairspring, or increasing the tension of the main spring, but does this have any implications in the day-to-day accuracy of the watch? Additionally, does this mean that the longevity of the movement is compromised?

Keep in mind that I am completely aware that we are talking about replica watches, and this is by all estimates, a VERY small factor to consider, but I am curious about what Clean has done to compensate for this, and what the implications of these differences are. Of course the obvious solution would be that if any inaccuracies bother me to just buy genuine replacements for these pieces, but I can't justify the price. For the cost of a genuine pallet fork, escape wheel and balance complete I could buy a dozen complete SH4131 movements. I'm just curious if anyone has thought of this, and if there are any issues stemming from these differences.

 

[kidcreole]

Good question but you could also direct this at the 4130 that also had a nonskeletonised escape wheel. It did OK along with every other similarly designed movement. I wouldn't worry about the SH accuracy but I'm also now intrigued why they went with a skeleton design. Perhaps it is slightly more efficient, better amplitude as you suggest or quieter?

 

[KJ2020]

As I understand it from Rolex's promotional releases concerning the thinner pallet stones and skeletonized escape wheel, their purpose is to conserve mainspring energy by reducing the amount needed to move those parts per tick.

So this would not affect amplitude or other performance parameters at all, just a slight increase to PR due to greater energy efficiency. I've seen claims of a 15% increase in energy efficiency, though I don't recall if Rolex was the source of that claim.

 

[sorginator]

Good question but you could also direct this at the 4130 that also had a nonskeletonised escape wheel. It did OK along with every other similarly designed movement. I wouldn't worry about the SH accuracy but I'm also now intrigued why they went with a skeleton design. Perhaps it is slightly more efficient, better amplitude as you suggest or quieter?

Rolex themselves said that they did it to extend the power reserve, which honestly doesn't really make a lot of sense to me. I guess their thinking is that because the pieces at the end of the wheel train are lighter and therefore take less force to move, they can increase the leverage of the mainspring (kind of like the overdrive gear in a car's transmission) so that each turn of the mainspring barrel equates to a greater number of vibrations on the other end. This, however, doesn't really make any sense because the old 4130 had the same power reserve as the 4131, yet the 4130 had a solid escape wheel.

 

[sorginator]

As I understand it from Rolex's promotional releases concerning the thinner pallet stones and skeletonized escape wheel, their purpose is to conserve mainspring energy by reducing the amount needed to move those parts per tick.

So this would not affect amplitude or other performance parameters at all, just a slight increase to PR due to greater energy efficiency. I've seen claims of a 15% increase in energy efficiency, though I don't recall if Rolex was the source of that claim.

Yes, apparently it was done to extend the power reserve, however it has the same 72 hour power reserve as the 4130 which doesn't have the skeletonized pieces. I'm thinking that Rolex is doing the same thing as Apple, where they put a super heavy emphasis on things that don't really make any difference in real life. I remember a few years ago, Apple made a huge deal of the fact that they used "airplane grade aluminum" for the sake of durability, but it made no real difference in the resilience iPhones have against damage from being dropped. They only did it for the sake of marketing, and for iPhone owners to brag about it to their friends.

Maybe I just don't understand (on a physics level) how skeletonized pieces extend the power reserve, but as it stands now I heavily suspect it is just a marketing thing. Rolex knows their customers well, and I doubt that the kind of person who buys Rolex watches actually know how they work and the engineering behind their movements. It sounds really good to say lightweight and skeletonized, but I don't see how this can impact power reserve. It might just have been done so people can brag about that change to 116500 (and older) owners.

But this still brings me back to the same question, the practical changes of the skeletonized pieces would only result in a greater balance wheel amplitude. I guess since the 4130 doesn't have the lightweight pieces and still has the same power reserve, it would suggest that the mainspring leverage would be the same, pointing to the conclusion that the 4130 would have less amplitude than the 4131. Since the 4130 movement had no fundamental inaccuracy problems, then it shouldn't cause any amplitude-induced issues in the day-to-day. The only thing that would confirm this presumption would be to compare the amplitudes of genuine 4130 and 4131 movements with the SH4131.

 

[KJ2020]

Rolex themselves said that they did it to extend the power reserve, which honestly doesn't really make a lot of sense to me. I guess their thinking is that because the pieces at the end of the wheel train are lighter and therefore take less force to move, they can increase the leverage of the mainspring (kind of like the overdrive gear in a car's transmission) so that each turn of the mainspring barrel equates to a greater number of vibrations on the other end. This, however, doesn't really make any sense because the old 4130 had the same power reserve as the 4131, yet the 4130 had a solid escape wheel.

It's probably largely a sales gimmick, much like Rolex's use of 904L steel. The ability to measure just the escapement "improvement" is greatly overshadowed by the longer mainspring, made available by thinning the barrel walls.

 

[sorginator]

It's probably largely a sales gimmick, much like Rolex's use of 904L steel. The ability to measure just the escapement "improvement" is greatly overshadowed by the longer mainspring, made available by thinning the barrel walls.

This makes a lot of sense. I think it is just a marketing thing and causes no real impact in the day-to-day. Typical marketers doing their thing...

 

[KJ2020]

But this still brings me back to the same question, the practical changes of the skeletonized pieces would only result in a greater balance wheel amplitude.

Assuming an identical diameter, the number of teeth in an escape wheel (the distance between each tooth) would affect amplitude, but if that parameter isn't different, the weight or construction of the parts would not.